發(fā)布時間：2019-05-15 18:05

【摘要】：鎳基單晶高溫合金具有優(yōu)異的高溫力學(xué)性能,瞬態(tài)液相(Transient liquid phase,簡稱TLP)連接方法是一種適于難以熔焊的高溫合金的連接技術(shù)。本文分別選用Ni-Cr-B和Ni-Cr-Si兩種合金粉末作為中間層合金對一種鎳基單晶高溫合金進(jìn)行TLP連接,研究了連接溫度和時間對接頭的組織和成分分布的影響,分析了TLP連接過程的等溫凝固行為,測試了接頭的硬度和剪切性能。Ni-Cr-B中間層合金TLP連接的接頭分為三個典型的區(qū)域:接頭中心的共晶區(qū)、位于共晶區(qū)兩側(cè)的等溫凝固區(qū)和位于近焊縫處基體中的擴(kuò)散影響區(qū)。在接頭中心的共晶區(qū)上形成Cr2B+γ和Ni3B+γ兩種共晶;等溫凝固區(qū)為γ鎳基固溶體;在擴(kuò)散區(qū)上形成M3B2析出相。隨連接溫度的升高或連接時間的延長,共晶區(qū)上的硼化物相逐漸減少,共晶區(qū)逐漸變窄;等溫凝固界面由接頭兩側(cè)向中心生長,等溫凝固區(qū)逐漸變寬;擴(kuò)散影響區(qū)的硼化物析出相繼續(xù)長大并向基體內(nèi)擴(kuò)散。為避免初熔現(xiàn)象的產(chǎn)生,TLP連接溫度和保溫時間應(yīng)在初熔轉(zhuǎn)變界線以下的條件選擇。TLP接頭在連接時間為2h時,隨連接溫度的升高接頭中心的硬度明顯降低;在連接溫度為1200℃時,TLP接頭隨連接時間的延長接頭中心硬度略有降低。升高連接溫度或延長連接時間有助于提升接頭的剪切強(qiáng)度,增加接頭的斷裂韌性,在1170℃保溫30min的條件下TLP接頭為脆性解理斷裂。Ni-Cr-Si中間層合金TLP連接的接頭由兩個區(qū)域組成:共晶區(qū)和等溫凝固區(qū),接頭中心共晶區(qū)上是Ni16Cr6Si7+γ和(Cr,Si)3Ni2Si+γ共晶,而等溫凝固區(qū)是含Si的鎳基固溶體。隨連接時間的延長或連接溫度的升高,共晶區(qū)寬度越窄,等溫凝固區(qū)寬度越寬,等溫凝固進(jìn)行的越充分。為避免初熔現(xiàn)象的產(chǎn)生,TLP連接溫度和保溫時間應(yīng)在初熔轉(zhuǎn)變界線以下的條件選擇。TLP接頭在連接時間為2h時,隨連接溫度升高接頭中心的硬度明顯降低;在1170℃下,TLP接頭隨連接時間增加接頭中心硬度略有降低。升高連接溫度或延長連接時間有助于提升接頭的剪切強(qiáng)度,增加接頭的斷裂韌性。在1170℃保溫30min的條件下TLP接頭為微孔聚集型韌性斷裂。
[Abstract]:Nickel-based single crystal superalloy has excellent high temperature mechanical properties. Transient liquid phase (Transient liquid phase, (TLP) bonding method is a kind of bonding technology suitable for difficult fusion welding of superalloy. In this paper, Ni-Cr-B and Ni-Cr-Si were used as interlayer alloys for TLP bonding of a nickel-based single crystal superalloy. The effects of bonding temperature and time on the microstructure and composition distribution of the joints were studied. The isothermal solidification behavior of TLP bonding process was analyzed, and the hardness and shear properties of the joints were tested. The joints connected by Ni-Cr-B interlayer alloy TLP are divided into three typical regions: the eutectic region in the center of the joint. The Isothermal solidification zone is located on both sides of the eutectic region and the diffusion affected zone is located in the matrix near the weld. Two kinds of eutectic, Cr2B 緯 and Ni3B 緯, were formed in the eutectic region of the joint center, and the M3B2 precipitated phase was formed in the isothermal solidification region of the solid solution based on gamma nickel and the precipitated phase of M3B2 in the diffusion zone. With the increase of bonding temperature or the prolongation of bonding time, the boride phase on the eutectic region decreases and the eutectic region narrows gradually, and the Isothermal solidification interface grows from both sides of the joint to the center, and the Isothermal solidification zone widens gradually. The precipitated phase in the diffusion affected region continues to grow and diffuses into the matrix. In order to avoid the phenomenon of initial melting, the connection temperature and holding time of TLP should be selected below the initial melting transition line. When the connection time is 2 h, the hardness of the joint center decreases obviously with the increase of connection temperature. When the connection temperature is 1200 鈩，

本文編號：2477693